1. Field of the Invention
The present invention relates to an ink jet recording head and manufacturing method thereof, and more particularly to an ink jet recording head provided with a filter preventing foreign matters from entering an ink flow path.
2. Description of the Related Art
The structure of a typical ink jet recording head will be described with reference to FIG. 8A. In the ink jet recording head illustrated in FIG. 8B, ink is discharged in an orthogonal direction relative to a discharge energy generating element 50 which generates energy for discharging ink.
Recently, in order to implement further downsizing and higher density of ink jet recording heads, there has been proposed a method of incorporating by use of a semiconductor manufacturing technique an electrical control circuit for driving the discharge energy generating elements into a substrate. The ink jet recording head illustrated in FIG. 8A is one manufactured by such technique. More specifically, in the substrate 51 illustrated in FIG. 8A, there are also incorporated an electrical control circuit (not illustrated) for driving the discharge energy generating elements 50, and other components.
Further, in order to supply ink to a plurality of ink discharge ports 52 through which ink is discharged, an ink flow path 53 is formed for each ink discharge port 52; and these ink flow paths 53 communicate with a common ink supply opening 54 formed in the substrate 51. The ink supply opening 54 extends through the substrate 51; and ink is supplied from the rear face side of the substrate 51 through the ink supply opening 54 to each ink flow path 53. When an Si substrate is used as the substrate 51, the ink supply opening 54 can be formed using an Si anisotropic etching technique (refer to U.S. Pat. No. 6,139,761).
Here, factors of reliability required of an ink jet recording head include one that printing failure ascribable to non-discharging (ink is not discharged from the particular nozzle) caused by nozzle blockage hardly occurs. As the typical reasons for occurrence of such printing failure, there are thought to be cutoff, etc., of ink to be supplied to the interior of the nozzle caused by solidification and dust entering the nozzle. Further, details of the latter reason are roughly classified as follows: (1) dust and foreign matters enter the nozzle during the ink jet recording head manufacturing process; or (2) dust and foreign matters come from the outside into the nozzle after the ink jet recording head manufacturing (during its use).
Particularly, regarding concern about the above reason (2), it is highly likely that when the ink supply system has a configuration separable from the ink jet recording head, dust and foreign matters come in through a connecting portion therebetween. As one measure against such reason, for example, there has been used a method of arranging a filter in the vicinity of the ink supply opening of ink jet recording head. However, in the case where a filter is arranged in the ink supply opening, when the filter is manufactured and mounted separately from the ink jet recording head, this is not always satisfactory in terms of manufacturing cost, component cost, quality control, connection reliability between components, or the like, resulting in requests for further improvement.
As an invention for solving these problems, Japanese Patent Application Laid-Open No. 2000-94700 has disclosed a technique of using an anisotropic etching mask for forming an ink supply opening in a substrate (Si substrate) to thereby form a filter. More specifically, as illustrated in FIG. 8A, a filter pattern is formed directly in a thermally-oxidized film layer 55 being the above anisotropic etching mask, and when the ink supply opening 54 is formed by anisotropic etching, a filter 56 is simultaneously formed using the thermally-oxidized film layer 55 which is an etching-resistant layer.
In the ink jet recording head disclosed in Japanese Patent Application Laid-Open No. 2000-94700, the filter 56 is arranged in the substrate rear face side opening portion of the ink supply opening 54; thus the filter 56 is exposed to the outside.
Consequently, during the post-process of forming the discharge energy generating element 50, the filter is exposed to various liquids, or when conveyed within the semiconductor manufacturing apparatus, minor flaws occur therein. Also, when the ink jet recording head is mounted, it is highly likely that minor flaws occur in the filter 56. As a result, for example, a pinhole 57 as illustrated in FIG. 8B occurs in the filter 56, thus reducing production yield or deteriorating filter performance.